1. Field of the Invention
The present invention relates to a semiconductor device including an oxide semiconductor and a method for manufacturing the same.
Note that in this specification, a semiconductor device refers to all devices that can function by utilizing semiconductor properties, and electro-optic devices such as display devices, semiconductor circuits, and electronic devices are all semiconductor devices.
2. Description of the Related Art
A light-transmitting metal oxide is used in a semiconductor device. For example, a conductive metal oxide (hereinafter referred to as an oxide conductor) such as an indium tin oxide (ITO) is used as a transparent electrode material needed in a display device such as a liquid crystal display.
In addition, a light-transmitting metal oxide has been attracting attention as a material having semiconductor properties. For example, an In—Ga—Zn—O-based oxide and the like are expected to be used as a semiconductor material needed in a display device such as a liquid crystal display. In particular, they are expected to be used for a channel layer of a thin film transistor (hereinafter also referred to as a TFT).
A TFT which includes a metal oxide having semiconductor properties (hereinafter referred to as an oxide semiconductor) can be formed through a low-temperature process. Thus, expectations for the oxide semiconductor as a material which replace or surpass amorphous silicon used in a display device and the like have been increased.
Further, both the oxide conductor and the oxide semiconductor have light-transmitting properties. Thus, when a TFT is manufactured using the oxide conductor and the oxide semiconductor, the TFT can have light-transmitting properties (for example, see Non-Patent Document 1).
Further, the TFT in which the oxide semiconductor is used has high field effect mobility. Thus, a driver circuit in a display device or the like can be formed using the TFT (for example, see Non-Patent Document 2).
[Reference]
    Non-Patent Document 1: T. Nozawa. “Transparent Circuitry”, Nikkei Electronics No. 959, Aug. 27, 2007, pp. 39-52.    Non-Patent Document 2: T. Osada et al., “Development of Driver-Integrated Panel using Amorphous In—Ga—Zn—Oxide TFT”, Proc. SID '09 Digest, 2009, pp. 184-187.